The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, the approaches described in this section may not be prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Many mobile devices, such as smartphones, tablet computing devices, personal digital assistants and laptop computers include a camera allow users to easily and quickly acquire photos and then share the photos with others via email, messaging and social network services. Despite the convenience provided by mobile devices equipped with a camera, there are some drawbacks. Unlike conventional cameras that allow a user to manually change the focus, or active focus cameras that use a separate sensor to measure focus, many mobile devices use passive auto-focusing to determine the correct focus without any user intervention. Passive auto-focussing generally involves capturing and evaluating images at different lens positions and selecting a lens position that provides the best sharpness, i.e., where adjacent pixels have the greatest difference in intensity, regardless of the image content. Passive auto-focussing does not work well with blurred images because the difference of intensity of adjacent pixels in blurred images is generally less than in clear images. It is not uncommon for users to experience delays and blurred images as they wait for the passive auto-focussing to complete and even after completed, an object of interest to a user may not be in the focus area. On many cameras and mobile devices, the default focus area is fixed at the center of the display and visually indicated by a focus area symbol, such as a rectangle, circle, etc., superimposed on the image. This forces a user to move or orient the mobile device so that an object of interest is within the focus area, as indicated by the focus area symbol, and then again wait for the passive auto-focus process to complete. Alternatively, some mobile devices allow a user to tap the screen at the location of an object of interest to move the focus area, and the corresponding focus area symbol, to that location. This avoids having to re-orient the mobile device so that the object of interest is in the center of the display, but requires that the user tap the screen.